Polyolefins are useful for a large variety of applications. These polymers are used to fabricate articles under conventional film blowing, injection molding and blow molding techniques. The molecular weight distribution of the polymer is a determinant in assessing whether the polymers are suitable for these various applications. For example, in injection molding, polyolefin polymers having a narrow molecular weight distribution are preferred. On the other hand, in blow molding, polyolefins having a broad molecular weight distribution are preferred.
Typically, unsupported catalysis systems have too small a particle size for commercial use. Supported catalysis systems are characterized by larger particle sizes and offer improved catalytic efficiency. Further, they are generally more stable and render higher molecular weight polymers.
Supports of the catalysis systems of the prior art, typified by silica gel, traditionally are used under slurry polymerization conditions. Unfortunately, it is often difficult to control the amount of catalyst on a silica gel support. In addition, silica gel is capable of deactivating certain catalysts and further may leave high concentrations of ash in the resulting polymer.
Further, the supported catalysis systems of the prior art are generally incapable of producing polyolefins with the requisite narrow molecular weight distribution needed for injection molding. In addition, such supported catalysis systems are heterogeneous in nature. As such, it is not uncommon for solid particulates or gels to become either deposited within the reactor or engulfed in the resultant polyolefin. The former, referred to as fouling, is often detrimental to the overall process since heat transfer is lost and the reactors typically must be shut down for a difficult cleaning process.
A need therefore exists for the development of a catalysis system which is homogeneous in nature, i.e., either liquid or capable of remaining in solution in the presence of an inert hydrocarbon, and which exhibits high thermal stability and which is capable of producing polyolefins of narrow molecular weight distribution.